The present invention relates to a radiometer which scans a background by means of a drivable optical system and at least one curved mirror element integral with this system, and directs thermal radiation to a detector facing it at a distance. It is equipped with an electronic system where a weighting evaluation corresponding to the position of detectors can be performed, and a threshold value makes possible conclusion on the degree of radiation, shown on a display unit, of the observed object.
From German Pat. No. 19 37 639 there is known a coverage degree meter which has the disadvantage that its mirror has large surfaces and is exposed to weather and dirt influences so that it must be equipped with a wiping device which can smear or even scratch the mirror surface. Because of the scanning principle used, long scanning times are required.
Accordingly, it is an object of the present invention to provide an improvement over the conventional equipment by avoiding the above-described disadvantages.
Another object of the present invention is to provide an arrangement of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide an arrangement, as described, which may be readily maintained in service and which has a substantially long operating life.